It is previously known to increase the range of fire for artillery shells, and also to decrease the time of flight for anti-aircraft and armour-piercing shells, by generation of a mass flow in the near wake zone, known as base flow or base bleed. This technique is based on that a fuel in the rear part of the projectile generates a mass flow, substantially gaseous, which flows out and usually is made subject to final combustion adjacent to the base plane of the shell/projectile. Utilized types of fuel, having good efficiency and suitable combustion rate (favourable drag reduction during a sufficient part of the flight period for the shell/projectile), are pressure sensitive, and the combustion initiated within the gun barrel by the gun powder gases is usually terminated due to the pressure drop caused when leaving the muzzle of the gun. The course of events can only to a minor extent be reproduced, resulting in an unwanted large dispersion with regard to impact point.
In order to secure reignition of the base bleed fuel, and to receive a reproducable result, a pyrotechnical charge of non-pressure sensitive type is used, known as an igniter. An example of a base bleed unit having such an igniter is disclosed in SE, A, 340 076. Other solutions to the reignition problem are also known, e.g. as disclosed in GB, A, 2 131 926 and DE, A1, 3 246 380, but these are mechanically complicated.
With previously known techniques, it is extremely difficult to change between the base bleed unit and a projectile extension of skirt type, since the utilized igniter is mounted by the base plane of the war head of the shell and with the open part of the igniter directed towards the outlet opening of the base bleed unit. For certain applications, a separate plate including the igniter has been located at the forward end portion of the base bleed unit, but this reduces, at a given total length, the space available for the base bleed charge or "payload" (e.g. explosives).